Australian Dental Journal The official journal of the Australian Dental Association Australian Dental Journal 2011; 56: 296–301 SCIENTIFIC ARTICLE doi: 10.1111/j.1834-7819.2011.01350.x Inhaled methoxyflurane (Penthroxâ) sedation for third molar extraction: a comparison to nitrous oxide sedation WA Abdullah,* SA Sheta,* NS Nooh* *Department of Oral and Maxillofacial Surgery, College of Dentistry, King Saud University, Riyadh, Saudi Arabia. Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Mansoura University, Mansoura, Dakahlia, Egypt. ABSTRACT Background: The aim of this study was to evaluate the use of inhaled methoxyflurane (PenthroxÒ) in the reduction of dental anxiety in patients undergoing mandibular third molar removal in a specialist surgical suite and compare it to the conventional nitrous oxide sedation. Methods: A prospective randomized, non-blinded crossover design study of 20 patients receiving two types of sedation for their third molar extraction who participated in 40 treatment sessions. At first appointment, a patient was randomly assigned to receive either nitrous oxide sedation or intermittent PenthroxÒ inhaler sedation, with the alternate regimen administered during the second appointment. Peri-procedural vital signs (heart rate and blood pressure) were recorded and any deviations from 20% from the baseline values, as well as any drop in oxygen saturation below 92% were documented. The Ramsay Sedation Scale (RSS) score was recorded every five minutes. Patient cooperation during the procedure, patients’ general opinion about the sedation technique, surgeon satisfaction and the occurrence of side effects were all recorded. After the second procedure, the patient was also asked if he or she had any preference of one sedation technique over the other. Results: Levels of sedation were comparable in nitrous oxide and PenthroxÒ sedation sessions. However, at 15 minutes of sedation it was significantly lighter (p < 0.05) in PenthroxÒ. No patient in both regimens reached a RSS deeper than a score of 4. Parameters measured for assessment of sedation (patient cooperation, surgeon satisfaction and patient general opinion about sedation technique) were all similarly comparable for both nitrous oxide and PenthroxÒ. In both sedation sessions, the odour of the inhalational agent was accepted by the patients; half of the patients (10 patients) who received methoxyflurane thought its odour was pleasant. Patients preferred methoxyflurane (PenthroxÒ) inhalation over nitrous oxide sedation (Fisher’s Exact test, p < 0.05). Adverse events were minimal. No patient was either deeply sedated or agitated. Blood pressure was within ± 20% from the baseline values. No patient had oxygen saturation less than 92%. Dizziness was the most frequently encountered side effect in both regimens (four patients each). Two patients had bradycardia (HR < 60 beats ⁄ minute) when nitrous oxide was used in comparison to one patient with PenthroxÒ sedation. Paraesthesia of fingers and heaviness of the chest was encountered only with nitrous oxide sedation (four patients). Mild self-limited shivering occurred in one patient with PenthroxÒ sedation. Conclusions: The PenthroxÒ Inhaler can produce a comparable sedation to that of nitrous oxide for the surgical extraction of third molars under local anaesthesia. Keywords: Inhaled methoxyflurane, PenthroxÒ, conscious sedation, third molar mandibular extraction. Abbreviations and acronyms: DAS-R = Dental Anxiety Scale, Revised; MAC = minimum alveolar concentration; PCS = patient controlled sedation; RSS = Ramsay Sedation Scale; VAS = Visual Analogue Scale. (Accepted for publication 1 December 2010.) so that the eventual treatment becomes more urgent INTRODUCTION and more costly, and often more difficult for the dentist Surgical removal of third molar teeth is the most because of anxiety-related patient behaviour during the common procedure in oral surgery.1 Studies have intervention.5 revealed that many patients who are about to undergo Inhalational sedation has unique advantages. Its surgical third molar removal experience high levels of onset of action is rapid and the effect can be maintained preoperative anxiety.2–4 This fear and anxiety can deter for as long as administration lasts.6 The depth of some patients from consulting, or delaying consultation sedation can be titrated and adjusted because the drug 296 ª 2011 Australian Dental Association Inhaled methoxyflurane sedation for third molar extraction is eliminated through the airway. Instead of a peak and were between the ages of 18 and 30 years. Patients effect, a plateau can be reached within a few minutes, who were morbidly obese or showed evidence of severe and recovery from the state of sedation occurs within renal impairment, hepatic disorder or obstructive minutes of ceasing administration. Currently, nitrous airway disease were excluded from the study. All oxide is the only available inhalational agent that meets married women were required to undergo a urine conscious sedation requirements. However, potential pregnancy test to ensure that they were not pregnant. occupational health hazards and the need for equip- Patients were discharged into the care of a responsible ment limits its use.6 adult and not permitted to drive or make decisions for Methoxyflurane (PenthroxÒ) was introduced as a 24 hours after the procedure. Patients answered general inhalational anaesthetic agent in the mid 1960s. Corah’s Dental Anxiety Questionnaire (DAS-R);15 The unique ability of methoxyflurane to cause effective patients with severe anxiety were excluded. Only those non-narcotic analgesia and anxiety relief at low who had a moderate or high level of anxiety according (subanaesthetic) concentrations was soon discovered.7 to the DAS-R were selected to take part in the study.15 The PenthroxÒ Inhaler is a simple plastic hand-held Radiological evidence was required to prove that all device for methoxyflurane inhalation, often referred to extractions for all patients (in both procedures) were of as the ‘Green Whistle’. Since 1978, ambulance services comparable difficulty. throughout Australia have administered methoxyflu- Standard preoperative instructions were given. All rane as a first-line analgesic agent.8 It has been used to patients were instructed to not eat or drink after progressively relieve anxiety and reduce pain in several midnight and were scheduled for morning appointments. clinical settings.8–12 The product is currently used in the However, unrestricted clear fluids were allowed for all Gulf Area, Eastern Europe, South-East Asia and Latin patients up to two hours before the procedure. All America. The PenthroxÒ Inhaler has recently been surgery was undertaken in a fully equipped oral and introduced to the Saudi market for the same purpose, to maxillofacial clinic with full resuscitation facilities and provide analgesia and anxiety relief. conducted by one of two maxillofacial consultants. Studies have long considered the use of inhaled Local anaesthesia was performed according to a stan- methoxyflurane (PenthraneÒ) for conservative dental dard protocol using a maximum of two (1.8 ml) carpules purposes. Methoxyflurane can produce analgesia and of 2% lidocaine with 1:80 000 epinephrine. Patients mood modifying properties,13 and improve operative were monitored via a non-invasive blood pressure cuff, conditions during dental procedures.14 three leads ECG and a pulse oximeter throughout the The aim of this study was to evaluate the use of entire procedure. Initial vital signs and oxygen saturation inhaled methoxyflurane (PenthroxÒ) in the reduction of were recorded and thereafter assessed every five minutes. dental anxiety in patients undergoing mandibular third Patients were randomly assigned to receive either molar removal in a specialist surgical suite and compare nitrous oxide sedation or PenthroxÒ Inhaler sedation it to conventional nitrous oxide sedation. for the first session. Before the proposed session, patients were instructed on the use of either the nasal mask for nitrous oxide sedation or the oral inhaler for Study design PenthroxÒ sedation. A prospective randomized, non-blinded crossover design was used with each subject serving as his own Nitrous oxide sedation session control. Twenty patients participated in 40 treatment sessions. At first appointment, a patient was randomly Nitrous oxide sedation was performed conventionally assigned to receive either regimen N (nitrous oxide in accordance with long-standing protocols of the sedation) or regimen P (PenthroxÒ Inhaler sedation) for Department of Oral and Maxillofacial Surgery. Ini- the first appointment, with the alternate regimen tially, 100% oxygen was delivered via a nasal mask, administered during the second appointment. and then nitrous oxide was gradually added, up to 30–50%, titrated to achieve a Ramsay Sedation Scale (RSS) score of 2 to 3 (Table 1).16 At the end of the METHODS procedure, 100% oxygen was given for three minutes The study was approved by the Local Ethics Committee before removal of the nasal mask. and all patients gave informed written consent. Partic- The PenthroxÒ Inhaler is a hand-held green plastic ipants included in the study were referred for third device, 15 cm in length with a mouthpiece at one end molar removal to the Department of Oral and Maxil- and a wick running through the centre. The contents of lofacial Surgery, College of Dentistry, King Saud the 3 ml glass bottle were poured onto the wick. The University, Saudi Arabia. inhaler was then shaken to dispel